This invention relates to apparatus for viewing photographic images previously recorded on a film-type medium and, more particularly, to such apparatus which converts film frame images to video signals for display on a video monitor, also known as a cine-video conversion system.
Film viewing mechanisms having general application such as film projection systems are well known to those of ordinary skill in the art, particularly in the field of cinematography or the like. These systems include a film transport mechanism and a projection mechanism, and typically project an illuminated image of one film frame at a time on a viewing screen or an empty wall. A constant image of one particular film frame may be viewed (as in a slide projector), or, more commonly, these systems are used to view images in motion. In particular, motion of the viewed A image may be perceived by the viewer as a result of the repetitive projection of successive film frames which were originally recorded on the film in rapid succession.
Film projection systems, however, suffer from several drawbacks and limitations. One such drawback is the problem of limited brightness, familiar to anyone who has been to a movie theater. This problem is inherent in the process of projecting light over a significant distance. Another limitation of merely projecting the light image of the film frame is the fact that since the image is never xe2x80x9ccapturedxe2x80x9d by the system, either electronically or otherwise, there is no possibility of processing or modifying the image to improve its quality or its usability.
Recently, cine-video systems which convert the images recorded on film to video signals in real time have been introduced as an alternative to standard film projectors. With this type of system, the film frame images are electronically xe2x80x9ccapturedxe2x80x9d, so as to be represented by electronic signals. These signals may be processed, if desired, and ultimately, they are displayed on a standard video monitor, thereby eliminating some of the drawbacks of projected images. The basics of such a cine-video system include a film transport mechanism, by which the film is loaded into the system and by which each film frame image is positioned for projection, a projection mechanism, by which the film frame image thus positioned is projected onto a video camera lens by an illuminating light source, and a video camera, by which the projected image is captured and converted to an electronic video signal.
One application of film viewing systems in general, and cine-video systems in particular, is in the medical field, and, more particularly, angiography, such as in a cardiac catheterization laboratory for producing high resolution displays on a standard video monitor from 35 mm angiographic film. In this application in particular, the lack of numerous quality and usability features, not heretofore present in either film projectors or prior cine-video systems, limits the value of these prior systems. For example, one of the major limitations of prior systems is the inability to provide for a continuously variable viewing speed (i.e., the number of consecutive film frames scanned by the film transport mechanism per second). In particular, although many of these systems allow for the viewing of motion at a few different film speeds, they generally do not provide for continuously variable speed viewing, as may be desired by the user, without loss of resolution.
Another drawback of the prior systems is their inability to electronically enhance the quality or usability of the video image. For example, and particularly in medical applications, it is often the case that the visibility of detail in the dark areas of high contrast pictures is limited. Electronic image enhancement techniques in which certain differences in brightness can be accentuated so as to provide more visibility of detail are not provided by prior systems. Although prior cine-video systems capture the image electronically and are therefore not inherently restricted from providing such capabilities as are mere film projectors, none have done so to date.
Yet another drawback of the prior systems is their high cost and inflexibility relative to the capabilities and features they provide. The manufacturing cost of mechanical designs and analog electrical circuitry implementation is far higher than the cost of digital electronics performing comparable functions. Moreover, the use of digital, programmable processors and associated software not only further reduces the cost, but also provides vastly superior flexibility, in that system functions can be added, replaced or modified easily and inexpensively. None of the prior commercially available film viewing systems, neither film projectors nor prior cine-video systems, are implemented as digital systems controlled by programmable digital processors.
A further drawback of prior systems is the lack of a direct digital video signal output, and particularly real time digital output, useful for applications such as recording on a digital VCR (video cassette recorder) or for data analysis. Whereas mere film projectors by themselves clearly cannot provide any output other than the viewable image itself, cine-video systems typically do provide video signal outputs. However, the prior cine-video systems do not provide any such output in a digital video format.
Yet another drawback of prior systems is the lack of a xe2x80x9cHi-linexe2x80x9d video signal output, which allows for the images to be viewed on a multi-scan monitor for improved quality. A Hi-line video signal provides for twice the standard number of scan lines, and thereby increases the image brightness as well as the apparent resolution, and further reduces the noticeability of raster scan lines. Again, whereas mere film projectors cannot provide output signals at all, cine-video systems do; however, the prior commercially available cine-video systems have provided only standard video signal outputs.
A still further drawback of prior systems is their inability to include user-locatable xe2x80x9ccursorxe2x80x9d marks overlaid on the image being viewed. Particularly in medical applications, and particularly when an image is being viewed and discussed by more than one medical professional, it is often useful to be able to precisely identify one or more points of particular interest on the image. Prior film viewing systems provide no mechanism for overlaying such identifying marks on the image, and therefore manual, imprecise tools, such as a hand-held pointer, must be used.
Yet another drawback of prior systems is the lack of any ability to provide measurement information regarding the distance between a pair of points on the subject of the image being viewed. Particularly in medical applications such as angiography, portions of the images viewed represent vessels or other anatomical elements whose absolute size or size relative to other elements is of critical importance. Prior film viewing systems provide no mechanism for making such measurements accurately, and therefore a combination of guesswork and manual, imprecise tools (e.g., a ruler used to measure portions of the viewed image itself) must be used.
Still another drawback of prior systems is the lack of an electronically controlled zoom capability for increasing and decreasing the magnification of the image being viewed. Prior systems have provided only imprecise, manual zoom capabilities, if at all.
These aforementioned drawbacks of prior film viewing systems, both film projectors and prior cine-video systems, reduce the effectiveness and flexibility with which one may view and make use of photographic images recorded on film. Particularly in medical applications such as angiography, the elimination of these drawbacks can provide for a far more powerful tool for film viewing and analysis for the professional user.
Therefore, it is an object of the present invention to provide an improved apparatus for viewing photographic images previously recorded on film, in particular, a cine-video system, which overcomes the aforementioned drawbacks and limitations associated with prior art film viewing apparatus.
Another object of this invention is to provide improved apparatus which permits film to be viewed in motion at continuously variable speeds without loss of resolution.
Another object of this invention is to provide cine-video apparatus in which the quality or usability of an image is enhanced by accentuating certain differences in brightness in order to provide improved visibility of detail.
A further object of this invention is to provide cine-video apparatus of low cost and high flexibility relative to its capabilities, by the use of digital electronics in general, and digital, programmable processors and associated software, in particular.
A still further object of this invention is to provide cine-video apparatus which includes a digital video signal output for use in recording on a digital VCR, for data analysis or for archiving purposes.
Still another object of this invention is to provide cine-video apparatus which includes a Hi-line video signal output containing twice the standard number of scan lines for improved viewing quality.
An additional object of this invention is to provide cine-video apparatus having user-locatable cursor marks overlaid on the image being viewed, in order to accurately locate and identify points of particular interest.
Yet a further object of this invention is to provide cine-video apparatus which includes the ability to provide measurement information regarding the distance between a pair of points on the subject of the image being viewed.
Still another object of this invention is to provide cine-video apparatus which includes an electronically controlled zoom capability for increasing or decreasing the magnification of the image being viewed.
Various other objects, advantages and features of the present invention will become readily apparent from the ensuing detailed description, and the novel features will be particularly pointed out in the appended claims.
In accordance with this invention, an apparatus for generating video signals from a photographic image previously recorded on film (a cine-video system) is provided, which includes a film transport mechanism for advancing or rewinding the film in order to position a film frame at a film gate for projection, an image projector which detects when a film frame is positioned at the film gate and projects an illuminated image of that frame, a video pickup system which receives the image and generates a video signal which represents it, and an output circuit which produces a resultant output video signal. Thus, a new image is received and a new video frame is generated, when a new film frame is positioned in the film gate.
As one aspect of this invention, the image projector is inhibited from projecting an illuminated image when the video pickup system is not ready to receive a new image. In this manner, the integrity of each image is assured, regardless of the speed with which the film transport mechanism is advancing or rewinding the film.
As another aspect of this invention, the image projector repetitively projects an illuminated image of the same film frame, when the film transport is holding the film frame fixed at the film gate but various user adjustments are being made to the resultant image. This aspect enables the viewer to see the effects of these adjustments, even though the system is in a xe2x80x9cstill frame mode.xe2x80x9d
As yet another aspect of this invention, the video pickup system includes provisions for the enhancement of the resulting video signal. This enhancement capability includes user-selectable gamma adjustment functions which accentuate the differences in brightness in the darker regions of the image, while compressing the differences in the brighter regions. This allows for greater visibility of detail in high contrast images.
Still another aspect of this invention provides a cine-video system which includes an image pickup system which receives a projected image and generates video signals which represent that image, a window generating capability with which the user can define a range of video signal values within which an enhancement of video signals is to be performed, and an enhancement capability which performs that enhancement. This user-selectable enhancement capability includes, for example, the ability to accentuate the differences in brightness within the given range of video signal values by xe2x80x9cstretchingxe2x80x9d this range of values into the full range of brightness values. Thus, the visibility of detail in a portion of the image of particular interest can be improved. Also included is the ability to invert the polarity of the image, thereby creating a xe2x80x9cnegativexe2x80x9d image, and the ability to perform a gamma adjustment within a selected window.
As yet another aspect of this invention, a cine-video system is provided which includes an image pickup system which receives a projected image and generates video signals which represent that image, a digitizer to convert these video signals to digital form, a memory for storing a video frame of digitized signals, an enhancement capability which enhances the digitized video signals if desired, and a digital signal processor which controls the image pickup system, memory and enhancement capability. By providing for a programmable, digital system, costs are reduced and flexibility is increased. This digital system may further include an output circuit which produces a video output in digital format.
Still another aspect of this invention is to provide a digital cine-video system which includes an optical zoom capability for zooming in and out on the image. By changing the magnification of the image in this manner, a particular area of detail may be examined more closely. The zoom capability is under the control of the digital signal processor.
Another aspect of this invention is to provide a digital cine-video system which includes an optical panning capability for panning the image. By using this feature in combination with the optical zoom capability, any portion of the image may be examined in detail. The panning capability is under the control of the digital signal processor.
As yet another aspect of this invention, a cine-video system is provided which includes an image pickup system which receives a projected image and generates video signals which represent that image, a memory in which the individual scan lines from the separate field intervals of the video signals generated for each film frame are separately stored, read-out circuitry by which the scan lines are read from the memory at twice the standard line repetition rate, and combining circuitry for selectively combining these lines of video signals from successive field intervals of at least one video frame to produce a resultant frame of video signals formed of twice the standard number of scan lines. Thus, a xe2x80x9cHi-linexe2x80x9d video signal is provided for use with video monitors which provides a significant increase in apparent resolution and reduces the noticeability of raster scan lines.
Another aspect of this invention is to provide a cine-video system which includes an image pickup system which receives a projected image and generates video signals which represent that image, a memory for storing a video frame, cursor generation circuitry for selectively generating one or more cursors, and circuitry to combine the video signals for the video frame with cursor signals to generate video signals which represent the image with one or more cursor overlays superimposed on the image. In this manner, a user may place cursors on the image at points of particular interest, for identification or discussion.
As still another aspect of this invention, the cine-video system includes a measurement capability with which the distance between two locations in the subject of the image can be determined by placing a cursor on the point in the image which corresponds to each such location. In one embodiment a calibration capability is provided for relating physical distances between locations in the subject of the image with distances in the image itself, thereby determining actual distance between the locations identified by the cursors. As an alternative, the measurement provides only relative distance information by comparing the distance between two locations in the subject of the image with the distance between another two such locations.